Self-powered relay target circuit

ABSTRACT

A relay target circuit is operated directly from the stored energy in a solid state relay circuit, after the relay circuit becomes conductive. Circuits are provided in which a-c and d-c control voltage sources are used and in which a diode is connected to the trip circuit to prevent a false set signal by transients in the tripping circuit. Parallel indicator circuits are used with a common reset switch.

White States Patent [191 Qonrad May 22, 1973 [54] SELF-POWERED RELAYTARGET [56] References Cited (IIRCUET UNITED STATES PATENTS [75]Inventor: Richard R. Conrad, Bristol, Pa.

3,573,556 4/1971 Zocholl ..317/33 SC [73] Assignee: l-T-E ImperialCorporation, Spri g 3,319,127 5/1967 Zocholl et a1. ..317/27 House, Pa.

. Primary Examiner-J. D. Miller 1 [22] Fl ed June 1972 AssistantExaminer-I-larry E. Moose, Jr. [21] Appl. No.: 260,750Attorney-Ostrolenk, Faber, Gerb & Soffen [63] Communion of 41,420 May1970 A relay target circuit is operated directly from the abandonedstored energy in a solid state relay circuit, after the relay circuitbecomes conductive. Circuits are pro- [52] US. Cl. ..317/33 SC, 317/27R, 31-7/151, vided in which and control voltage Sources are 340/248 R253R used and in which a diode is connected to the trip cir- Cl. cuit toprevent a false Set signal transients in the [58] Field of Search..340/253 R, 253 A,

340/253 M, 248 R, 248 B, 253 P; 317/27, 149,151, 33 SC tripping circuit.Parallel indicator circuits are used with a common reset switch.

3 Claims, 5 Drawing Figures l jff 65/ I a /34 3 I 25 I 7? I Z 7 I 07 756 04/5 lfiisfr 574/? awa /r5 5.4a

I jaw/76% 720 f awa /r SELF-POWERED RELAY TARGET CIRCUIT RELATED CASESThis is a continuation of application Ser. No. 41,420 filed May 28,1970, now abandoned.

This invention is an improvement of copending application Ser. No.826,932, filed May 22, 1969, now U.S. Pat. 3,573,556, in the name ofZocholl, entitled Operation Indicator Circuit for Static OvercurrentRelays, and assigned to the assignee of the present invention, and is tobe used with solid-state relay circuits of the type shown in U. S. Pat.No. 3,319,127 to Zocholl et al.

SUMMARY OF INVENTION The stored energy of a solid-state relay circuit isused for operating an indicating device for indicating the firing of acontrolled rectifier associated with the solidstate relay circuit. Theindicator circuit operates to a set condition even though control poweris lost. Either a-c or d-c control power can be used, and more than asingle indicator circuit can be provided.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a circuit diagram of oneembodiment of the invention.

FIG. 2 shows the circuit of FIG. 1 modified for a-c control power.

FIG. 3 shows the circuit of FIG. 1 modified for parallel-indicatorcircuit operation.

FIG. 4 shows a further embodiment of the invention.

FIG. 5 shows the modification of FIG. 4 for parallelcircuit operation.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there isshown, in part, a solid-state type relay which includes a d-c input atterminals 20 and 21, which could be derived, for example,

from the rectified output of a current transformer (not' shown),connected to a circuit being monitored. Current-limiting resistor 22,filter capacitor 23 and zener diode 24 then form a reference voltagesource for the operation of the solid-state relay, and the constantvoltage across terminals 25 and 26 is then used to drive other parts ofthe solid-state relay in a manner not pertinent to the presentinvention. The controlled rectifier 27 is the controlled rectifier whichis fired from the relay circuit and is connected to the trip circuitoutput terminal 28 to effect, for example, disconnection of the circuitbeing monitored in response to given fault conditions.

In the following, it will be seen that the relay components required foruse with the present invention are the constant voltage reference sourcecapacitor 23 and controlled rectifier 27.

The target circuit of the present invention includes use of the set coil30 and reset coil 31 connected, as shown, which operate indicator 32,where these coils are operated from the relay stored energy. Coil 30 andreset coil 31 may be the device known as an electromagnetic statusindicator, made by Ferranti-Packard Electric Ltd., of Toronto, Canada.This device is built as a three-terminal device having one coil with acenter tap. The rated drive requirement is a 4.2 volt d-c, 250milliampere pulse, lasting for l millisecond for each coil, set orreset. These coils are magnetically coupled to an indicator which ismoved between an indicating and non-indicating position, responsive toindication of the set or reset coil, respectively. Devices of this typeare shown in copending application Ser. No. 826,932, now U.S. Pat. No.3,573,556 noted above.

Diode 35 is connected in series with set coil 30 to block current fromterminal 20, through set coil 30 and into the reference circuit. Diode36 is connected in series with terminal 28 to prevent false setindications originating in the external tripping circuits when trippingis initiated by external circuits.

In order to operate the reset coil 31, a momentary switch 37 isprovided, connected in series with coil 31. The common terminal of thereference voltage circuit is then connected to terminal 21 throughresistor 38.

In operation, it is assumed that indicator 32 is in a non-indicatingposition, and that the circuit being monitored is operated through thesolid-state relay circuit. That is, a firing signal is applied to thegate of controlled rectifier 27. The firing of controlled rectifier 27permits the passage of a pulse from capacitor 23, through set coil 30,diode 35, controlled rectifier 27, and back to the negative side ofcapacitor 23. Indicator 32 will then operate to an indicating position,indicating that controlled rectifier 27 has fired. After energization ofthe trip circuit, the controlled rectifier 27 will extinguish, theresistor 38 being large enough to limit current between terminals 20 and21 to below the hold ing current of controlled rectifier 27.

The target or indicator 32 is reset by closing contact 37 anddischarging capacitor 23 through reset coil 31. Note that capacitor 23can recharge through resistor 38 if the trip circuit is open but theterminals 20 and 21 are energized.

FIG. 2 is similar to FIG. I, but shows the circuit using a-c controlpower rather than d-c control power. In FIG. 2, components similar tothose of FIG. I are given similar identifying numerals. An a-c inputcircuit of this type is disclosed in copending application Ser. No.673,583, filed Oct. 9, 1967, now U.S. Pat. No. 3,478,250, in the name ofZocholl et al, entitled Static A.C. Switching Circuit, and assigned tothe assignee of the present invention. In the circuit of FIG. 2, controlpower is taken from a-c terminals 40 and 41a, which are connected to therectifier bridge including diodes 41 to 44. Diodes 45 and 46 connect thecircuit output to trip circuit terminal 28. An a-c holding resistor 47performs the recharge function of resistor 38.

FIG. 3 illustrates the manner in which the circuit of the invention canbe used when the indication must show which of two (or more) differentmodes of tripping initiated the trip. Thus, such a relay might have botha time-delay element and an instantaneous element, with separate targetsto indicate which element operated. In FIG. 3, components similar tothose of FIG. 1 have similar identifying numerals. FIG. 3, however,shows two controlled rectifiers 50 and 51 which are tripped responsiveto different conditions, such as instantaneous trip and time-delay trip,respectively.

A respective pair of set and reset coils 52-53 and 54-55 are providedfor controlled rectifiers 50 and 51, respectively, each pair connectedto respective indicator targets 56 and 57, respectively. Diodes 58 and59 are connected in series with controlled rectifiers 50 and 51 todirect set pulses to the appropriate set coil. Diode 60 serves thefunction of diode 35 of FIG. 1. A single reset switch 61 is provided forreset coils 53 and 55, although separate reset switches could have beenused.

The operation of the circuit of FIG. 3 is similar to that of FIG. 1,except that the two indicator systems including indicators 56 and 57 arein parallel.

It should be noted that the circuit of FIG. 3 could be modified to usea-c control voltage in the manner described in FIG. 2. 7

FIG. 4 illustrates a modification of the invention for the case wherecontrol power is not used to operate the relay circuits. Thus, this typecircuit is used, for example, with overcurrent relay circuits whoseinternal circuitry is operated solely from an input signal derived fromthe overall current condition itself. The set function is stillaccomplished as in FIG. 1, but the circuit and indicator are modified toperform the reset function.

In FIG. 4, components similar to those of FIG. 1 are given similaridentifying numerals. FIG. 4, however, provides a single set and resetcoil 70, formed of the series connection of the set and reset coils ofFIGS. 1 to 3, where these coils operate indicator 71. A diode 72 isprovided to block current flow into the solid-state circuit from thecontrol voltage terminal 20, while allowing a set pulse to flow fromcapacitor 23, through coil 70, in a set direction, and throughcontrolled rectifier 27, responsive to firing of controlled rectifier27.

Reset operation is obtained in FIG. 4 by closing reset switch 80, toallow current flow from terminal 20 through coil 70 in the resetdirection, through currentlimiting resistor 81 and into capacitor 82.Resistor 81 is chosen to limit the peak-current value of this dischargecurrent while resistor 83 discharges capacitor 82 after reset switch 80operates.

It is to be noted that with the circuit of FIG. 4, the target circuit atpoint A can be connected to other energy sources within the solid-statecircuit, such as level measuring filters, or directly to the signal Vbeing monitored, if the proper minimum voltage and currents areavailable.

If desired, the circuit of FIG. 4 could be modified for operation witha-c input, rather than d-c input in the manner shown generally in FIG.2.

FIG. 5 illustrates the manner in which the circuit of FIG. 4 can beadapted for operation with two or more indicator sections. Thus, in FIG.5, and in the manner of FIG. 3, two indicators 90 and 91, cooperatingwith coils 92 and 93, respectively, are provided for controlledrectifiers 94 and 95, respectively, which fire responsive to differentconditions. As in FIG. 3, each of the controlled rectifiers 94 and 95 isconnected in series with diodes 96 and 97, respectively. Clearly, thecircuit of FIG. 5 could use a-c control power when modified as shown inFIG. 3.

Although this invention has been described with respect to its preferredembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. In combination, a solid-state relay and an indicator circuit; saidsolid-state relay including circuit means for monitoring the operationof an electrical circuit, a controlled rectifier fired responsive to apredetermined circuit condition in said electrical circuit, a capacitorcircuit for defining a voltage reference for said solid-state relayincluding a capacitor charged to a given voltage and a reference zenerdiode connected in parallel with said capacitor, an output trip circuit,and means connecting said controlled rectifier and output trip circuitin circuit relation; said indicator circuit comprising a set coil, areset coil, and indicator means connected to said set coil and resetcoil and operable to a set condition and reset condition responsive toenergization of said set coil and reset coil, respectively, a resetswitch, and a diode; said set coil connected in series with said diode,said capacitor and said controlled rectifier; said reset coil connectedin series with said capacitor and said reset switch; and a source of d-cvoltage derived from said circuit means for monitoring the operation ofan electric circuit connected across said capacitor.

2. The combination of claim 1, wherein said set and reset coils areconnected in series with one another.

3. The combination of claim 2, which further includes a secondcontrolled rectifier and second set and reset coils and an indicatormeans for said second controlled rectifier.

1. In combination, a solid-state relay and an indicator circuit; saidsolid-state relay including circuit means for monitoring the operationof an electrical circuit, a controlled rectifier fired responsive to apredetermined circuit condition in said electrical circuit, a capacitorcircuit for defining a voltage reference for said solid-state relayincluding a capacitor charged to a given voltage and a reference zenerdiode connected in parallel with said capacitor, an output trip circuit,and means connecting said controlled rectifier and output trip circuitin circuit relation; said indicator circuit comprising a set coil, areset coil, and indicator means connected to said set coil and resetcoil and operable to a set condition and reset condition responsive toenergization of said set coil and reset coil, respectively, a resetswitch, and a diode; said set coil connected in series with said diode,said capacitor and said controlled rectifier; said reseT coil connectedin series with said capacitor and said reset switch; and a source of d-cvoltage derived from said circuit means for monitoring the operation ofan electric circuit connected across said capacitor.
 2. The combinationof claim 1, wherein said set and reset coils are connected in serieswith one another.
 3. The combination of claim 2, which further includesa second controlled rectifier and second set and reset coils and anindicator means for said second controlled rectifier.